This overview of residential energy efficiency is appropriate for future auditors, would-be retrofitters, and anyone else who lives in a house. It starts with the basics of heat, air and moisture flow. Various insulation and air sealing materials are discussed. Heating fuels, heating systems, and hot water systems are compared. Common building performance problems and their solutions are outlined. There is a brief description of blower door testing and related diagnostics, along with suggestions for prioritizing recommendations. Condensation, indoor air quality, and combustion safety are briefly covered. No previous technical knowledge is needed.